title: Cadmium-induced oxalate secretion from root apex is associated with cadmium exclusion and resistance in Lycopersicon esulentum.
abstract: The mechanisms of heavy metal resistance in plants can be classified into internal tolerance and exclusion mechanisms, but exclusion of heavy metals with the help of organic acids secretion has not been well documented. Here we demonstrated the contribution of oxalate secretion to cadmium (Cd) exclusion and resistance in tomato. Different Cd resistance between two tomato cultivars was evaluated by relative root elongation (RRE) and Cd accumulation. Cultivar 'Micro-Tom' showed better growth and lower Cd content in roots than 'Hezuo903' at different Cd concentrations not only in short-term hydroponic experiment but also in long-term hydroponic and soil experiments, indicating that the genotypic difference in Cd resistance is related to the exclusion of Cd from roots. 'Micro-Tom' had greater ability to secrete oxalate, suggesting that oxalate secretion might contribute to Cd resistance. Cd-induced secretion of oxalate was localized to root apex at which the majority of Cd accumulated. Phenylglyoxal, an anion-channel inhibitor, effectively blocked Cd-induced oxalate secretion and aggravated Cd toxicity while exogenous oxalate supply ameliorated Cd toxicity efficiently. These results indicated that the oxalate secreted from the root apex helps to exclude Cd from entering tomato roots, thus contributes to Cd resistance in the Cd-resistant tomato cultivar.
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Xiao Fang
authors.initials: XF
authors.lastname: Zhu
authors.forename: Cheng
authors.initials: C
authors.lastname: Zheng
authors.forename: Yi Ting
authors.initials: YT
authors.lastname: Hu
authors.forename: Tao
authors.initials: T
authors.lastname: Jiang
authors.forename: Yu
authors.initials: Y
authors.lastname: Liu
authors.forename: Ning Yu
authors.initials: NY
authors.lastname: Dong
authors.forename: Jian Li
authors.initials: JL
authors.lastname: Yang
authors.forename: Shao Jian
authors.initials: SJ
authors.lastname: Zheng
mesh_terms: D002104:Cadmium / Q000378:metabolism / Q000494:pharmacology*; D018551:Solanum lycopersicum / Q000737:chemistry / Q000187:drug effects* / Q000254:growth & development; D010070:Oxalates / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010658:Phenylglyoxal / Q000494:pharmacology; D053147:Plant Exudates / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry / Q000187:drug effects* / Q000254:growth & development; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development; D012987:Soil / Q000737:chemistry
chemical_list: D010070:Oxalates; D053147:Plant Exudates; D012987:Soil; D002104:Cadmium; D010658:Phenylglyoxal